German Patent Application No. 36 09 428 is directed to "A Method and a Device for Testing Devices of a Motor Vehicle for a Fault-Free Condition". It concerns the detecting and storing of faults, both with respect to the input and output signals, as well as to the internal signal processing of a control unit, and the outputting of the same in response to a request signal. Specifically, the memory, into which possible fault signals are written, is queried on a block by block basis in response to a request signal and, moreover, there is a ranking of the faults when they are output to the display.
German Patent Application No. 40 38 972 is directed to a "Device for Computing a Motor-Vehicle Service Interval". It provides for various operational values to be recorded, such as number of starts, crankshaft revolutions, driving and parking times, engine temperature, engine oil pressure and the like, and for the service interval to be calculated from the values by a computer. This makes it possible for the driver to specify a service interval that is oriented to the specific operating conditions of the vehicle, so that he or she will be signaled when there is an actual need to have the vehicle serviced.
Finally, U.S. Pat. No. 4,939,652 relates to a "trip recorder", which makes it possible to indicate operational data to the driver, to record the data and, subsequently, to process them in an "off-line computer". This trip recorder must be a type of "black box", as is also provided in airplanes to protect data in the event of a crash.
A considerable cost factor is entailed by motor-vehicle control units. For that reason, efforts have often been made to increase their reliability and to reduce their probability of failure. However, because of the per se rough operation of a motor vehicle, mechanical, electrical, and external thermal influences constitute a certain potential for danger to a control unit. Therefore, an object of the present invention is to create a device which will allow statements to be made regarding the failure probability or the future reliability of a control unit.